1 -- 创建表并插入数据：
2 create table tb
3 (
4 name varchar ( 10 ),
5 val int ,
6 memo varchar ( 20 )
7 )
8 insert into tb values
9 ( ' a ' , 2 , ' a2(a的第二个值) ' ),
10 ( ' a ' , 1 , ' a1--a的第一个值 ' ),
11 ( ' a ' , 3 , ' a3:a的第三个值 ' ),
12 ( ' b ' , 1 , ' b1--b的第一个值 ' ),
13 ( ' b ' , 3 , ' b3:b的第三个值 ' ),
14 ( ' b ' , 2 , ' b2b2b2b2 ' ),
15 ( ' b ' , 4 , ' b4b4 ' ),
16 ( ' b ' , 5 , ' b5b5b5b5b5 ' )
1 -- 一、按name分组 取 val最大 的值所在行的数据。
2 -- 方法1：
3 select a. * from tb a where val = ( select max (val) from tb where name = a.name) order by a.name
4 -- 方法2：
5 select a. * from tb a where not exists ( select 1 from tb where name = a.name and val > a.val)
6 -- 方法3：
7 select a. * from tb a,( select name, max (val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name
8 -- 方法4：
9 select a. * from tb a inner join ( select name , max (val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name
10 -- 方法5
11 select a. * from tb a where 1 > ( select count ( * ) from tb where name = a.name and val > a.val ) order by a.name
1 -- 二、按name分组 取 val最小的值所在行的数据。
2 -- 方法1：
3 select a. * from tb a where val = ( select min (val) from tb where name = a.name) order by a.name
4 -- 方法2：
5 select a. * from tb a where not exists ( select 1 from tb where name = a.name and val < a.val)
6 -- 方法3：
7 select a. * from tb a,( select name, min (val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name
8 -- 方法4：
9 select a. * from tb a inner join ( select name , min (val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name
10 -- 方法5
11 select a. * from tb a where 1 > ( select count ( * ) from tb where name = a.name and val < a.val) order by a.name
1 -- 三、用开空函数row_number() over()
2 SELECT * FROM (SELECT*,ROW_NUMBER() OVER( PARTITION BY name ORDER BY val DESC ) rid FROM tb) AS t WHERE rid = 1
